A. Technical Field
The present invention relates to a production process for a catalyst. More particularly, the present invention is intended for the production process for a catalyst which is utilized for various chemical reactions (e.g. reforming, cracking, (amm)oxidation, and reduction of hydrocarbons) in the form such that a catalytic component (e.g. metal elements) is supported on a carrier.
B. Background Art
Catalysts in the form such that a catalytic component is supported on a particulate lump carrier (such catalysts may hereinafter be referred to simply as “supported catalysts”) can efficiently be brought into contact with a liquid or gaseous substance as a reactant or are easy to handle. Therefore, such catalysts are widely utilized as catalysts for production of various chemicals.
As a process for supporting the catalytic component onto the carrier, there is known a process including the steps of: charging a treatment container with a particulate lump carrier and a solution or powder of a catalyst precursor as a source for supplying the catalytic component; and then stir-mixing them together. By this stir-mixing treatment, the catalyst precursor adheres to or is impregnated into outer surfaces of the carrier and/or the inside of pores of the carrier, so that the catalytic component is supported onto the carrier. By carrying out heat treatment at the same time as or after the stir-mixing, there is also carried out the following: to provide the catalytic activity; or to remove liquid components and/or salts from the catalyst precursor; or to strengthen the bonding force of the catalytic component to the carrier.
There has hitherto been known a process for supporting the catalytic component onto the carrier with various types of supporting treatment apparatuses. Some examples thereof include: a process that involves using a revolving-dish type apparatus such that a dish-shaped treatment container is revolved around the rotational axis to thereby tumble the carrier in the treatment container (for example, refer to Patent Document 1 and Patent Document 2 below); and a process that involves using a revolving-cylinder type apparatus such that a cylindrical treatment container is revolved around the rotational axis to thereby tumble the carrier (for example, refer to Patent Document 3 and Patent Document 4 below). In addition, other examples include a process that involves using a fluidized-bed granulation apparatus such that a liquid catalytic component is sprayed onto a carrier as fluidized by a gas stream (for example, refer to Patent Document 5 and Patent Document 6 below).                [Patent Document 1]                    JP-A-315147/1988                        [Patent Document 2]                    JP-A-299797/1996                        [Patent Document 3]                    JP-A-279030/1994                        [Patent Document 4]                    JP-B-015176/1983                        [Patent Document 5]                    JP-A-000930/1983                        [Patent Document 6]                    JP-A-031171/1994                        
As to the catalysts for production of various chemicals (e.g. products, such as acrylic acid, methacrylic acid, ethylene oxide, phthalic anhydride, and maleic anhydride), their catalytic performances (e.g. the activity upon raw substances and the selectivity of the objective product) are naturally given priority. However, for industrially using the catalysts, it is ideal for them to satisfy all conditions such as the physical strength and the cost of producing the catalysts (e.g. yield and expense for operation).
As to the aforementioned conventional process for supporting the catalytic component onto the carrier by the stir-mixing, there are problems such that: the supporting ratio is low, and the production yield of the objective catalyst is low, and the physical strength of the supported catalyst is low.
As to the aforementioned apparatus carrying out the stir-mixing simply by revolving the treatment container (e.g. revolving-dish type apparatus and revolving-cylinder type apparatus), the stirring efficiency of the carrier and the catalyst precursor is not very good, and therefore, the ununiformity in the adhesion of the catalyst precursor to the carrier takes place, so that the dispersion occurs to the particle diameters of the catalyst as obtained by the supporting treatment. Particularly, in the case of the revolving-dish type apparatus that has hitherto most generally been used, the treatment is carried out in the dish type treatment container having a large area, and therefore a large quantity of the catalyst precursor remains adhering to the innef surface of the treatment container without being supported on the carrier. As a result, there are the problems such that: the production yield of the catalyst is low, and the physical strength of the catalyst is also low.
As to the fluidized-bed granulation apparatus, the resultant catalysts (particulate catalysts) violently collide with each other due to the gas stream, and therefore the catalytic component is easily peeled off.
Usually in the production of the catalyst, even if the carrier and the catalyst precursor are strongly stirred, the supporting of the catalytic component onto the carrier does not become better. In the case where the stirring is too strong like in such as the aforementioned fluidized-bed granulation apparatus, the catalytic component is rather not supported well. On the other hand, also in the case where the stirring is too weak, the uniformity or the yield is lowered, for example, because the catalyst precursor is locally supported onto the carrier or adheres to the treatment container.